Pressurized fuel injection system



Jan. 17, 1961 s. H. MICK PRESSURIZED FUEL INJECTION SYSTEM 2Sheets-Sheet 1 Filed March 5, 1958 XMSTK. w 5Q my D Av Wm? i m Q QATTOPA/6Y Jan. 17, 1961 s. H. MICK PRESSURIZED FUEL INJECTION SYSTEM 2Sheets-Sheet 2 Filed March 5, 1958 IN VENTOR. Sfanfe 71(77FtkPRESSURIZED FUEL INJECTION SYSTEM Stanley H. Mick, St. Clair Shores,Mich, assignor to General Motors Corporation, Detroit, Mich, acorporation of Delaware Filed Mar. s, 1958, Ser. No. 119,439

Claims. Cl. 261-23) The present invention relates to a mechanism forpressurizing a fuel system. More specifically, the present inventionrelates to a mechanism for pressurizing a fuel injection systemutilizing an atmospheric nozzle of the type shown in copendingapplication Serial No. 591,889, Dolza, filed June 18, 1956.

It is becoming increasingly necessary to provide pressurized fuelsystems in order to avoid serious problems, such as vapor lock, whichattend the use of higher volatility fuels. It has long been commonknowledge that by pressurizing a fuel system, e.g. maintaining a closedsystem and pressurizing the fuel therein, it is possible to eliminatethe tendency of the fuel to vaporize Within the system. Many suchpressurized fuel systems are available.

Previous types of pressurized fuel systems generally employ pressureopening nozzles and are, therefore, inapplicable in the case of a fuelinjection system utilizing a continuously open atmospheric type nozzle.More specifically, an atmospheric type nozzle is normally disposed in anintake passage such that it is exposed to variations in manifolddepression. Unless provision was made therefor, such manifold depressionwould tend to disrupt or unduly influence the quantity of fuel suppliedto the nozzle. To prevent this occurring an envelope of atmospheric airis provided at a point within the nozzle where the fuel stream is to bedirected into the intake passage. In this way the effect of manifoldvacuum is neutralized since the fuel stream is sprayed from the nozzleat all times at substantially atmospheric conditions.

The difficulties of pressurizing a system using such atmospheric nozzlesbecomes apparent when it is realized that if the fuel only ispressurized the nozzle fuel orifice sizes would have to be considerablyreduced in size in order to maintain the desired air-fuel ratio. Sincesuch fuel orifice size is already extremely small, e.g. .011", andrepresents a critical part of such system both from manufacturing andclogging viewpoint, it is apparent that further reduction in fuelorifice size would be most undesirable.

The present invention represents a unique and yet sim ple means ofpressurizing such a fuel system without the necessity of changing thefuel orifice size from that presently in use. In the present device acommon source of air under pressure is provided and the air therefromutilized to pressurize the fuel and at the same time pressurize thereference air provided to the atmospheric nozzle. In this Way apreviously non-pressurized fuel system may be readily adapted forpressurized operation by simply adding air pressurizing means in themanner taught by the present invention.

Other objects and advantages of the present invention are set forth inthe description which follows.

In the drawings:

Figure 1 is a partially sectioned view of a fuel system embodying thesubject invention; and

Figures 2 and 3 are enlarged detail views.

2,968,4Y3 Patented Jan. 17, 1961 While the present invention may beadapted for use with any fuel system employing an atmospheric nozzle,for the purposes of illustration the invention is incorporated in a fuelinjection system of the mass air flow type substantially as shown anddescribed in the aforenoted copending Dolza application.

Briefly, the fuel injection system includes an air intake passage ithaving a tapered diffuser element 12 disposed therein and cooperatingtherewith to define an annular venturi 14. A throttle valve 16 isdisposed in the intake passage and which passage communicates with airplenum chamber 18. A plurality of intake passages 20 communicate theplenum chamber with each of the individual cylinders 22 of an internalcombustion engine. A fuel metering mechanism is provided generally at 24and includes a fuel reselyoir 26 supplied with fuel from an inletconduit 23. The fuel level in reservoir 26 is controlled, in aconventional manner, by a float controlled inlet valve 30. A pump 32 isprovided Within the fuel reservoir and is adapted to supply fuel underpressure to a fuel metering valve indicated generally at 34. The fuelmetering valve in turn supplies fuel through a conduit 36 to adistributor 38 from which individual fuel conduits iii deliver fuel tonozzies 42 disposed in each of the intake passages 20.

The fuel metering valve 34 includes a member 44 slidably disposed in acasing 46 and which member is adapted to coact with a spill or bypasspassage 48 to control the quantity of fuel supplied to outlet conduit36. Thus, as the slidable valve element 44 moves to uncover spillpassage 48 less fuel is supplied to conduit as and conversely as thespill passage is progressively restricted the quantity of fuel suppliedto conduit 36 is increased. The slidable valve element 44 is operativelyconnected through a linkage device 56) to a metering control diaphragm52 suitably mounted in the fuel reservoir casing The actuation ofdiaphragm 52 is determined by the mass of air flow through venturi l4.Venturi 14- is communicated with an annular chamber 56 within which iscreated a vacuum force proportional to mass air flow. This vacuum forceis then communicated with the diaphragm 52 through a conduit 58.Accordingly, as the mass of air fiow through the intake passage 12increases, the increased vacuum force in conduit 58 causes diaphragm 52to be moved upwardly moving the slidable valve element 44 downwardly toprogressively restrict the spill passage 48.

Referring to Figure 3 it will be seen that the atmospheric nozzles 42includes a casing portion 60 mounted upon the end of fuel conduit 46. Apair of arially spaced orifices 62 and 6 3 are formed in casing 60.Orifice 62 is a fuel metering orifice which is adapted to target a fuelstream throughthe larger air metering orifice 64. A plurality ofradiating passages 66 are formed through casing cc and centrally definea space or chamber 68 which is maintained at whatever pressure obtainswithin a manifold '79 commonly communicating with all the nozzles 42. inthe non-pressurized version of the subject system, as described in theafo-renoted Dolza applicahen, the manifold 7d and nozzle chamber 68weremaintained at substantially atmospheric condition whereby manifoldvacuum acting on the shroud end 72 of nozzle 512 would be neutralized soas to have no effect on the quantity of fuel flowing through themetering orifice 62.

In order to pressurize the present fuel system, a suitable source of airunder pressure is provided. While any suitable air pressurizing meansmay be utilized, a single cylinder compressor 74, as best seen in Figure2, has been illustrated. A compressor piston 7c may be convenientlydriven from a single throw crankshaft 78 which may also be utilized todrive fuel pump 32. Compressor '74 further includes spring biased inletand outlet valves 80 and 82. Outlet valve 82 is adapted to communicatewith a conduit 84 to supply air under pressure to pressure storage tank86. A supply conduit 88 leads from the storage tank 86 and may includesuitable pressure relief valve 90. While any reasonable air pressure maybe maintained, for purposes of illustration, valve 99 may be set for 25psi.

It is desirable to supply air to inlet valve 80 through a conduit 81connecting at its other end with induction passage intermediate venturi14 and throttle lie. In this way air flow through the venturi isincreased which insures a strong vacuum metering signal on diaphragm 52.

Air under pressure is supplied to nozzle air manifold 70 and from thereconduit 92 pressurizes the fuel in reservoir 26. Since the fuel isplaced under 25 psi, it is necessary to create a corresponding backpressure at nozzle 42, as an alternative to reducing the size of nozzlefuel orifice 62, to maintain the desired fuel flow rate. This backpressure is achieved supplying the nozzle manifold air from supplyconduit 83, supra. in this way the fuel system may be maintained undersufficient pressure to prevent fuel vaporization therein withoutinterfering with the fuel flow rate otherwise determined by the fuelmetering mechanism.

In a non-pressurized system the nozzle air metering orifice 64 might beapproximately .040". However, in pressurizing the reference airsuppliedto nozzles, supra, it becomes necessary to reduce the size oforifice 64 in order not to increase the engine idling speed by supplyingexcess idle air. Thus, when pressurizing to 25 p.s.i., given as anexample, it would be necessary to reduce the air metering orifice toapproximately .028". Even as reduced, however, the orifice 64 is stillsubstantially larger than fuel metering orifice 62.

Inasmuch as reservoir 26 is maintained under superatmospheric pressure,e.g. 25 p.s.i., a reasonably good seal must be maintained between thereservoir and lower diaphragm chamber 53 in order not to upset themetering function of diaphragm 52. This is achieved by providing asuitable seal 55 between diaphragm control rod 57 and reservoir casing54. Additionally, chamber 53 is vented substantially to atmosphericpressure through a conduit 59 communicating with induction passage 10anteriorly of venturi 14. In these ways it is insured that actuation ofdiaphragm 52 will be in accordance with mass air flow through venturi14.

It is, of course, apparent that the output pressure of fuel supplied bypump 32 to reservoir 26 must exceed the superatmospheric pressureapplied to the reservoir by compressor 74.

It is apparent that the invention as illustrated may be modified oradapted to other fuel systems within the scope of the hereinafterappended claims,

I claim:

1. A charge forming device for an internal combustion engine comprisingan air intake passage, a throttle valve in said passage, a plurality ofinduction passages communicating said intake passage with the individualcylinders of the engine, a fuel nozzle in each of said inductionpassages, a fuel metering mechanism for supplying metered quantities offuel to each of said nozzles, said metering mechanism including a fuelreservoir, each of said nozzles comprising a fuel metering orifice, an

air metering orifice axially spaced from said fuel metering orifice, anair chamber intermediate said orifices, a common air manifoldcommunicating the respective nozzle air chambers, a source of air undersuperatmospheric pressure, conduit means communicating said air pressuresource, said air manifold and said fuel reservoir whereby said nozzleair chambers and said reservoir are maintained under superatmosphericpressure.

2. A charge forming device for an internal combus tion engine comprisingan air intake passage, a throttle valve in said passage, a plurality ofinduction passages communicating said intake passage with the individualcylinders of the engine, a fuel nozzle in each of said inductionpassages, a fuel metering mechanism for supplying metered quantities offuel to each of said nozzles, said metering mechanism including a fuelreservoir, each of said nozzles comprising a fuel metering orifice, anair metering orifice axially spaced from said fuel metering orifice, anair chamber intermediate said orifices, a common air manifoldcommunicating the respective reference air chambers, and means formaintaining said air manifold and fuel reservoir under superatmosphericpressure.

3. A charge forming device for an internal combats-- tion engineincluding an intake passage for each engine cylinder, a fuel nozzledisposed in each intake passage proximate the associated enginecylinder, said nozzle including an air chamber through which fuel issprayed prior to entering the intake passage, means for supplying:metered quantities of fuel to each nozzle, said means in eluding a fuelreservoir, and means for maintaining eacls nozzle air chamber and fuelreservoir under superatmospheric pressure.

4. A charge forming device as set forth in claim 3 in. which thesuperatmospheric pressure maintaining means comprises an air pump, areservoir for storing the air. under pressure from said pump, andconduit means inter-- connecting said air reservoir, said nozzle airchambers and said fuel reservoir.

5. A charge forming device for an internal combustion engine comprisingan air intake passage, a throttle valve in said passage, a plurality ofinduction passages communicating said intake passage with the individualcylinders of the engine, a fuel nozzle in each of said inductionpassages, a fuel metering mechanism for sup-- plying metered quantitiesof fuel to each of said nozzles, said metering mechanism including afuel reservoir, a pump in said reservoir for supplying fuel under pres--sure to said nozzles, each of said nozzles comprising a fuel meteringorifice, an air metering orifice axially spaced. from said fuel meteringorifice, an air chamber inter-- mediate said orifices, a common airmanifold communicating the respective reference air chambers, a pump forpressurizing air, a pressurized air reservoir, conduit meanscommunicating said air reservoir, said air manifold and said fuelreservoir, and common drive means for said fuel and air pumps.

References Cited in the file of this patent UNITED STATES PATENTS2,711,720 Nallinger June 28, 1955 2,829,873 Kupka Apr. 8, 1958 2,860,859Dolza Nov. 18, 1958

